Help Please. O2 Sensor CEL (1 Viewer)

[flobro]

Hello. I’ve been fighting a CEL for my B2S2 for a few weeks. Would love some more input. I had another thread but couldn’t figure out how to edit. This one has more info and pictures and video.
In the video, Car is warmed up @ idle. Long Term Fuel trim is black and red lines, o2 voltage is yellow & blue. I changed out sensor with a new Denso, same result. Ordered another new Denso thinking I got a bad one. Same result. On the test drive the fuel trim is about 12-15% off from one bank to the other. B2S2 voltage stays at .8v almost the whole time, although sometimes it does return to .02v when coasting.

Here’s what I have done so far.
-Cleaned the MAF with maf cleaner
-Checked spark plugs and coils in bank 2
-Cecked b2s2 wires for continuity @connector to ecm
-Replaced o2 sensor with new Denso two times
-Air filter is clean
-Voltage on both upstream sensors is around 3.1v
-Catalytic converter temperature is same on both sides

The LX470 is a MY2006. I have a 2000 LC so I can swap parts from one car to another if parts interchange. Just tell me what to try.
YouTube videos

 

[white_lx]

(Original post: P0158 Code even after sensor replacement. - https://forum.ih8mud.com/threads/p0158-code-even-after-sensor-replacement.1289444/)

Your three (3) different S2B2 O2 sensors demonstrated the same behavior (original + 2 replacements). So, we can probably safely assume they are showing the correct information. Stuck at high voltage (but not over 0.9V) means you have a rich condition on Bank 2. You said you can smell it too? Do you smell the fuel from the exhaust?

S1 sensor is an A/F for the 2006MY (not an O2 sensor) It is possible that S1B2 is reading incorrectly even though it looks like is working fine. The result can be too much fuel trim to get to the happy 3.3V spot with the observed result of S2B2 stuck rich.

Do you have access to Techstream? It has an active test function that allows trimming injected volume by +/- 12.5%. This is the best method to test if the A/F sensor is working properly. With -12.5% trim your S2B2 should go lean. What is the S1B2 at those conditions?

Alternative method to test the A/F sensor: Graph S1B1 and S1B2 and do some snap throttles. They should go rich (lower than 3.3V) to lean (higher than 3.3V) to stoich (3.3V). Compare S1B1 and S2B2.

You could also swap B1 and B2 A/F sensors and see if the rich condition moves to bank 1.

 

[flobro]

White_lx thank you for your reply. I hope it helps the next guy in the future. I did swap the B1S1 sensor (a/f) and the problem switched to other side. So long story short, and much headache it ended up being a bad air fuel ratio sensor. The front ones. I do not have techstream yet, but I did just order the cable. I’m in the middle of figuring out if it’s gonna work with my MacBook Pro.

 

[white_lx]

Thanks for posting the update. Failed A/F sensors can report what seem to be normal values an can be somewhat difficult to diagnose.